Direct bandgap semiconductor bonded to silicon photonics

ABSTRACT

According to an example of the present disclosure a direct bandgap (DBG) semiconductor structure is bonded to an assembly comprising a silicon photonics (SiP) wafer and a complementary metal-oxide-semiconductor (CMOS) wafer. The SiP wafer includes photonics circuitry and the CMOS wafer includes electronic circuitry. The direct bandgap (DBG) semiconductor structure is optically coupled to the photonics circuitry.

BACKGROUND

Photonics is the field of technology relating to the generation,transmission, reception and manipulation of light. Photonic devicesinclude for example waveguides, splitters, combiners,wavelength-division multiplexing (WDM) structures, mirrors, gratings,lasers, photodetectors, optical amplifiers, optical modulators, opticalfilters, optical resonators etc. Silicon photonics (SiP) relates tophotonic devices which are based on silicon and has the potential toprovide high quality, low cost photonic devices built using silicon chiptechnologies.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the disclosure will now be described, by way of non-limitingexample, with reference to the accompanying drawings, in which:

FIG. 1 is a flowchart showing an example method according to the presentdisclosure;

FIG. 2 is a schematic diagram showing an example assembly according tothe present disclosure;

FIG. 3 is a schematic diagram showing an example assembly according tothe present disclosure;

FIG. 4A is a flowchart showing an example method according to thepresent disclosure;

FIG. 4B is a schematic diagram showing an example of bonding of aSilicon photonics (SiP) wafer to a Complementary metal oxidesemiconductor (CMOS) wafer;

FIG. 4C is a schematic diagram showing an example assembly according tothe present disclosure;

FIG. 5A-5C are schematic diagrams showing example assemblies accordingto the present disclosure;

FIG. 6A-6B are schematic diagrams showing example assemblies accordingto the present disclosure;

FIG. 7 is a flowchart showing an example method according to the presentdisclosure;

FIGS. 8A to 8F are cross sectional diagrams showing examples of variousstages of manufacture of an assembly according to the method of FIG. 7;

FIG. 9 is a flowchart showing an example method according to the presentdisclosure;

FIGS. 10A to 10E are cross sectional diagrams showing examples ofvarious stages of manufacture of an assembly according to the method ofFIG. 9;

FIG. 11A is a schematic cross sectional diagram showing an example ofbonding of a direct bandgap (DBG) semiconductor wafer to an assemblycomprising a SiP wafer and a CMOS wafer according to the presentdisclosure;

FIG. 11B is a schematic cross sectional diagram showing an example of ahybrid photonics-electronics wafer assembly according to the presentdisclosure;

FIG. 11C is a schematic cross sectional diagram showing an example of ahybrid photonics-electronics wafer assembly according to the presentdisclosure;

FIG. 11D is a schematic cross sectional diagram showing an example ofcutting the assembly of FIG. 11C into separate hybrid photonicelectronics integrated chips according to the present disclosure;

FIGS. 12A to 12C are schematic diagrams showing examples of hybridphotonic electronics integrated chips according to the presentdisclosure;

FIGS. 13 to 16 are cross sectional diagrams showing examples of opticalcoupling according to the present disclosure;

FIG. 17 is a cross sectional diagram along the x-y axis showing anexample of a hybrid photonics electronics integrated chip according tothe present disclosure;

FIG. 18 is a cross sectional diagram along the y-z axis showing anexample of a hybrid photonics electronics integrated chip including aDBG horizontal cavity laser according to the present disclosure; and

FIG. 19 is a cross sectional diagram along the y-z axis showing anexample of a hybrid photonics electronics integrated chip including aDBG VCSEL according to the present disclosure.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the present disclosure isdescribed by referring mainly to examples thereof. As used herein, theterms “includes” means includes but not limited to, the term “including”means including but not limited to. The term “comprises” means includesbut not limited to, the term “comprising” means including but notlimited to. The term “based on” means based at least in part on. Theterm “number” means any natural number equal to or greater than one. Theterms “a” and “an” are intended to denote at least one of a particularelement. The term “connected to” means “connected directly or indirectlyto”, the term “connects to” means “connects directly or indirectly to”.Several examples and diagrams refer to layers of an assembly and theirrelative positions. Positioned over means positioned above and includesdirectly above and above with one or more layers in between. Positionedunder means positioned below and includes directly below and below withone or more layers in between. It is to be understood that each layermay itself comprise one or more sub-layers.

Complementary metal oxide semiconductor (CMOS) fabrication is awell-established technology for manufacturing silicon based electronicintegrated circuits. Due to many years of research such electronic ICscan now be manufactured at a large scale, at low unit cost with highreliability and with very small transistor sizes.

Silicon photonic (SiP) devices may be manufactured by processing asilicon substrate to sub-micro meter precision. Complementary metaloxide semiconductor (CMOS) fabrication lines may be used to form the SiPdevices thereby leveraging existing production lines and many years ofexperience with CMOS fabrication techniques. However, the manufacturingenvironment for CMOS fabrication is very tightly specified andcontrolled and many substances are forbidden on a CMOS production line.

Silicon, Germanium and other CMOS compatible semiconductors have anindirect bandgap. An indirect band gap semiconductor is a semiconductorin which the maximum energy of the valence band occurs at a differentvalue of momentum to the minimum energy of the conduction band. As suchindirect bandgap semiconductors are suitable for constructingwaveguides, gratings and mirrors, but are not optimum for theconstruction of light emitting and light detecting devices. Certainphotonic devices, especially lasers, but also photodetectors and others,are best implemented using direct bandgap semiconductors. A directbandgap (DBG) semiconductor is a semiconductor in which the maximumenergy of the valence band and the minimum energy of the conduction bandoccur at the same value of momentum. Direct bandgap semiconductorsinclude, but are not limited to, Group III-V semiconductors and GroupII-VI semiconductors. A Group III-V semiconductor is a semiconductorincluding at least one element from Group III or Group V of the PeriodicTable. A Group II-VI semiconductor is a semiconductor including at leastone element from Group II or Group VI of the Periodic Table. Many directbandgap semiconductors are compound semiconductors, which aresemiconductors composed of two or more elements.

In general, direct bandgap semiconductor materials, such as Group III-Vmaterials, are not allowed on a CMOS production line. Furthermore,certain materials such as gold, which are often used as electricalcontacts for direct bandgap semiconductor devices, are not allowed on aCMOS production line.

Accordingly, one example of the present application proposes a methodincluding receiving an assembly comprising a SiP wafer which has beenbonded to a CMOS wafer. The SiP wafer is a wafer which includes photoniccircuitry, wherein at least some of the photonic circuitry includessilicon. The CMOS wafer is a wafer which includes electronic circuitry,at least some of the circuitry including a metal-oxide-semiconductorstructure. The electronic circuitry may include silicon. The methodcomprises bonding a direct bandgap (DBG) semiconductor structure to theSiP wafer. Because the DBG semiconductor structure is bonded to the SiPwafer after the SiP wafer has been bonded to the CMOS wafer, the bondingof the DBG semiconductor structure to the SiP wafer may be carried outon a different production line, or at the back end of the productionline, so as not to contaminate the CMOS manufacturing facilities.

The DBG semiconductor structure may be optically coupled to the photoniccircuitry in the SiP wafer and electrically connected to the electroniccircuitry in the CMOS wafer. In one example, the DBG semiconductorstructure is controlled by the electronic circuitry and generates lightthat is to be directed to the photonics circuitry. In another examplethe DBG semiconductor structure detects an optical signal received fromthe photonic circuitry and sends an electrical signal based on theoptical signal to the electronic circuitry for processing.

FIG. 1 is a flow diagram showing a method 10 according to one example ofthe present disclosure.

At block 110 of method 10, an assembly 100 including a SiP wafer 300which has already been bonded to a CMOS wafer 200 is received. Theassembly 100 may for example be received by a production line, orsection of a production line, which is to carry out processes such asthose described in any of blocks 120-140 described below.

The SiP wafer 300 and CMOS wafer 200 may have been bonded together toform the assembly at an earlier stage of the manufacturing process,prior to block 110, as is described in more detail later. An example ofthe assembly 100 comprising the CMOS wafer 200 bonded to the SiP wafer300 is shown in FIG. 2.

The CMOS wafer 200 comprises electronic circuitry 201. The electroniccircuitry 201 includes at least one logic device, such as a transistor,logic gate, processor etc. The electronic circuitry may also includeelectronically conductive lines to connect logic devices of theelectronic circuitry together and/or to connect the electronic circuitrywith devices external to the CMOS wafer, as will be described in moredetail later. The electrical circuitry may further comprise resistors,capacitors, inductors, high speed analogue circuitry etc. The electroniccircuitry 201 may have been fabricated on the CMOS wafer in a previousprocess on another production line, or at an earlier stage of the sameproduction line.

The SiP wafer 300 comprises photonics circuitry 301. The photonicscircuitry 301 may include one or more photonic devices, such as but notlimited to an waveguides, optical splitters, optical combiners,wavelength-division multiplexing (WDM) structures, mirrors, gratings,lasers, photodetectors, optical amplifiers, optical modulators, opticalfilters, optical resonators. In some examples the photonics circuitryincludes a plurality of photonic devices at least some of which are toperform different optical functions to each other. The photoniccircuitry 301 may have been fabricated on the SiP wafer in a previousprocess on another production line, or at an earlier stage of the sameproduction line.

At block 120 of method 10, a direct bandgap (DBG) semiconductorstructure is bonded to the SiP wafer. Any suitable bonding method may beused including, but no limited to, molecule bonding, metal bonding,polymer bonding etc. Molecule bonding is a method in which a surface ofthe DBG semiconductor structure is bonded directly to a surface of theSiP wafer. Molecule bonding may include exposing the surfaces to somesurface activation process, e.g. a plasma, to facilitate the bonding,prior to placing the surfaces in contact with each other. Moleculebonding may result in good optical properties such that coupling oflight between the DBG semiconductor structure and the SiP wafer is notdisrupted.

The DBG semiconductor structure includes a direct bandgap semiconductormaterial. In one example the DBG semiconductor material is a group III-Vsemiconductor material. In one example the DBG semiconductor material isa group II-VI semiconductor material. In one example the DBGsemiconductor material is a compound semiconductor. The DBGsemiconductor structure may include a number of layers and may include aplurality of different semiconductor materials. In one example the DBGsemiconductor structure includes at least one material selected from thegroup comprising: indium phosphide (InP), gallium arsenide (GaAs),Indium gallium arsenide (InGaAs), indium arsenide (InAs), aluminumgallium arsenide (AlGaAs), indium gallium arsenide phosphide (lnGaAsP),indium gallium aluminum arsenide (InGaAlAs), indium gallium arsenidenitride (lnGaAsN), indium gallium phosphide (InGaP), indium aluminumarsenide (InAlAs), indium antimonide (InSb), aluminum antimonide (AlSb),aluminum arsenide antimonide (AlAsSb), indium gallium antimonide(InGaSb) and indium gallium aluminum antimonide (InGaAlS).

In one example, the DBG semiconductor structure comprises a photonicsdevice. In another example the DBG semiconductor structure comprises anunprocessed or partially processed die which may be further processed,after bonding to the SiP wafer, to form a photonics device. Thephotonics device may be a light emitting or light detecting device suchas a laser, photodetector, optical modulator or optical amplifier etc.

In some examples there may be additional processes between receiving theassembly 100 in block 110 and bonding the DBG semiconductor structure400 to the assembly 100 in block 120. For example, a substrate of theSiP wafer 300 of the assembly 100 may be removed before bonding the DBGsemiconductor structure 400 to the SiP wafer. This and examples of otherprocesses are described in more detail later.

At block 130 of method 10, the DBG semiconductor structure is opticallycoupled to the photonics circuitry in the SiP wafer. In this context,“optically coupling” the DBG semiconductor structure to the photonicscircuitry in the SiP wafer means forming an optical structure by whichan optical signal may be coupled in at least one direction between theDBG semiconductor structure and the photonics circuitry. This may makeit possible for an optical signal generated by the DBG semiconductorstructure to be transferred to the photonics circuitry and/or for anoptical signal in the photonics circuitry to be transferred to the DBGsemiconductor structure for detection.

The optical coupling of block 130 may form part of the bonding processof block 120 or may be a contemporaneous process or a subsequentprocess. For instance, the bonding process of block 120 may includealigning pre-existing optical structures of the SiP wafer withpre-existing optical structures of the DBG semiconductor structure tocreate an optical coupling between them. In other examples, at least oneof the DBG semiconductor structure and the SiP wafer may be furtherprocessed after the bonding of block 120 to form optical structureswhich create the optical coupling. The optical coupling of the DBGsemiconductor structure to the photonics circuitry may comprise formingan optical path including at least one of an evanescent couplingstructure, a grating, a mirror and an angled facet. Examples aredescribed in more detail later.

At block 140 of method 10, the DBG semiconductor structure iselectrically connected to the electronic circuitry 201 in the CMOS wafer200. This may allow the electronic circuitry 201 to at least one of:control operation of the DBG semiconductor structure and receiveelectrical signals from the DBG semiconductor structure. In one example,electrically connecting the DBG semiconductor structure to theelectronic circuitry of the CMOS wafer may include connecting anelectrical contact of the DBG semiconductor structure with a via thatextends at least partially through the SiP wafer.

FIG. 3 shows an example of a hybrid photonics-electronics assembly 500formed by the method 10 of FIG. 1. In the context of this disclosure,the term “hybrid” means that the assembly includes both a DBGsemiconductor structure and silicon photonics. The assembly 500comprises a SiP wafer 300 including photonics circuitry 301, which isbonded to a CMOS wafer 200 including electronic circuitry 201. A DBGsemiconductor structure 400 is bonded to surface of the SiP wafer 300.The SiP wafer 300 is positioned between the DBG semiconductor structure400 and the CMOS wafer 200. More specifically the SiP wafer 300underlies the DBG semiconductor structure and overlies the CMOS wafer200. This allows for convenient optical coupling between the DBGsemiconductor structure 400 and the photonic circuit 301 in the SiPwafer 300. Furthermore, the DBG semiconductor structure 400 and theelectronic circuitry 201 of the CMOS wafer 200 may generate significantheat, so positioning them at the top and bottom of the assembly mayfacilitate dissipation of heat to the surrounding environment or to aheat sink mounted to the top or bottom of the assembly. In this respectpositioning the DBG semiconductor at the top of the assembly may beespecially convenient, as it allows the heat generating DB G to be incloser contact with a heat sink, therefore allowing efficient heatextraction.

The DBG semiconductor structure 400 is electrically connected to theelectronic circuitry 201 of the CMOS wafer by an electrically conductiveline 202 and optically coupled to the photonic circuitry 201 of the SiPwafer as indicated by arrow 302. It should be noted that the opticalcoupling may be in one direction or both directions.

It will be appreciated that the method 10 of FIG. 1 comprises receivingan assembly 100 including a CMOS wafer and a SiP wafer which havealready been bonded together. FIG. 4A is a flow diagram showing aprevious stage 5 of the manufacturing process prior to FIG. 1. Thus atblock 102 of FIG. 4A a SiP wafer is bonded to a CMOS wafer. This isshown schematically in FIG. 4B where a SiP wafer 300 including photoniccircuitry 301 is bonded to a CMOS wafer 200 including electroniccircuitry 201. The bonding at block 102 may be molecule bonding, metalbonding or polymer bonding etc. The bonding may form a strong mechanicalconnection between the CMOS wafer 200 and SiP wafer 300 such that theyare fixed in place relative to each other. In some examples, the bondingmay form an electrical connection 203 between the photonics circuitry301 and the electronic circuitry 201 as shown in FIG. 4C. For example,respective surfaces of the CMOS wafer and the SiP wafer which are to bebonded together may include electrically conductive contacts which arealigned with each other when the CMOS wafer is bonded to the SiP wafer.This may allow the electronic circuitry to control the photoniccircuitry and/or to send/receive electrically transmitted data or othersignals to/from the photonic circuitry. In one example the bonding ofthe SiP wafer to the CMOS wafer is flip chip bonding. Flip chip bondingis a technique in which one wafer is flipped over so that its topssurface faces downwards and is bonded to the top surface of anotherwafer, as shown in FIG. 4B.

FIG. 5A is a schematic diagram showing another example of a hybridphotonics-electronics assembly 510 formed by the method 10 of FIG. 1. Itis the same as the example of FIG. 3, except that it shows an electricalconnection 203 between the CMOS electronic circuitry 201 and the SiPphotonic circuitry 301, as well as an electrical connection 202 betweenthe CMOS electronic circuitry 201 and the DB G semiconductor structure400. Thus FIG. 3 shows an arrangement in which the CMOS electroniccircuitry 201 is not connected to the SiP photonic circuitry. This maybe useful where the SiP photonic circuitry comprises passive photonicdevices such as waveguides. FIG. 5A shows an arrangement in which thereis an electrical connection 203 between the CMOS electronic circuitry201 and the SiP photonic circuitry 301 and may be useful where thephotonic circuitry 201 includes an active photonic device or a pluralityof active photonic devices.

FIG. 5B is a schematic diagram showing a further example of a hybridphotonics-electronics assembly 520 formed by the method 10 of FIG. 1. Itis the same as the example of FIG. 5A, but shows the photonic circuitry301 in more detail. The photonic circuitry 301 comprises a plurality ofphotonic devices at least some of which perform different photonicfunctions to each other. The plurality of photonic devices includes afirst photonic device 301A and a second photonic device 301B. In thisexample, the first photonic device 301A is optically coupled to the DBGsemiconductor structure, but is not electrically connected to theelectronic circuitry 201 of the CMOS wafer. The second photonic device301B is electrically connected to the electronic control circuitry, butis not optically coupled to the DBG semiconductor structure. Forexample, the DBG semiconductor structure 400 may be a light generatingdevice such as a laser, the first photonic device 301A may be a passivephotonic device such as a waveguide which is to receive light generatedby the DBG semiconductor structure, and the second photonic device 301Bmay be an active photonic device, such as an optical modulator, which isoptically coupled to the first photonic device.

In general, a passive photonics device is a device which performs anoptical function without using electrical power, while an activephotonics device is a device which uses electrical power to interactwith the light in the desired fashion. The photonics circuitry maycomprise a plurality of active and passive photonic devices and theactive photonic devices may be electrically connected to the CMOSelectronic circuitry 201.

It will be appreciated that some implementations of the presentdisclosure may include complicated photonics circuitry including manyphotonic devices which operate under control of sophisticated CMOSelectronic circuitry. Furthermore, the photonics circuitry may make useof an active DBG photonics device which is optically coupled to thephotonics circuitry and may be controlled by the CMOS electroniccircuitry. Possible applications include, but are not limited to, anoptical transmitter or optical receiver and dense wavelength divisionmultiplexing (DWDM). Furthermore, the CMOS electronic circuitry mayinclude logic circuitry to perform complicated signal encoding anddecoding operations. According to some implementations of the presentdisclosure, such a device may be provided on a single hybridphotonics-electronic integrated chip and may be manufactured at scale byusing semiconductor fabrication techniques.

FIG. 5C is a schematic diagram showing another example of a hybridphotonics-electronics assembly 530 formed by the method 10 of FIG. 1. Itis the same as the example of FIG. 3, except that it shows an example ofthe DBG semiconductor structure 400 in more detail.

The DBG semiconductor structure 400 shown in FIG. 5C includes an activelayer 420 positioned between a first cladding layer 410 and a secondcladding layer 430. For example, the first cladding layer 410 may bebonded to an upper surface of the SiP wafer 300, the active layer 420may be positioned over the first cladding layer 410 and the secondcladding layer 430 may be positioned over the active layer 420. Whiledepicted as single layers for clarity in FIG. 5C, it is to be understoodthat each of the first cladding layer 410, active layer 420 and secondcladding layer 430 may include one or more layers.

The active layer 420 may be a layer which is to generate or amplifylight in response to application of an electric potential, or togenerate an electrical current in response receiving photons. The activelayer may, for example, be a gain region of a laser, amplifier ormodulator. In one example, the active layer 420 is a quantum well layerand may include one or more quantum wells or quantum dots. The claddinglayers 410 and 430 may at least partially optically confine photonswithin the active layer 420. The cladding layers may be positively ornegatively doped. In one example the cladding layers and active layertogether form a p-i-n structure. At least the active layer 420 is formedof a DBG semiconductor material. The cladding layers 410, 430 may alsocomprise a DBG semiconductor material of the same, or a different, type.The DBG semiconductor structure 400 may, for example, be a blankepitaxial die which is to be processed to form a DBG photonic device, ormay be a partially or fully processed die. In some examples, the DBGsemiconductor structure 400 may include the active layer 420 and thecladding layer 430 which is above the active layer, but not the claddinglayer 410 which is below the active layer. In such examples the activelayer 420 may be bonded directly to the upper surface of the SiP wafer300. In that case one of the dielectric layers in the SiP wafer, e.g.layer 330 or 310, may act as the lower cladding layer.

FIG. 6A is a schematic diagram showing an example structure of aCMOS-SiP wafer assembly 100, such as the assembly manufactured in FIG.4A, in more detail. The CMOS wafer 200 includes a substrate 210 and anelectronic circuitry layer 201 positioned over the substrate. The SiPwafer 300 comprises a photonics layer 320 which includes the photonicscircuitry 301 and an electrical interconnect layer 310 which ispositioned under the photonics layer 320. One side of the electricalinterconnect layer 310 may be adjacent the photonics layer 320 and theother side may be bonded to the CMOS wafer 200. The electricalinterconnect layer 310 includes at least one electrically conductiveline 203 which is embedded in electrically insulating material 204. Theelectrically conductive line 203 may connect the photonic circuitry 301with the electronic circuitry 201 of the CMOS wafer 200. Anotherelectrically conductive line 202 is shown in FIG. 6B which includes avia extending from the interconnect layer 310 through the photonicslayer 320 to an upper surface 305 of the photonics wafer 300. The viamay later form part of an electrical path linking the electroniccircuitry 201 to the DB G semiconductor structure 400 (not shown in FIG.6A) which is later to be bonded to the upper surface 305 of the SiPwafer.

In another example, the electrically conductive line 202 may connect theelectronic circuitry 201 of the CMOS wafer 200 to an electrical contactwhich is to receive power from an external power supply. In anotherexample, the electrically conductive line 202 may connect the electroniccircuitry 201 to an electrical contact for receiving electrical controlsignals from, or sending electrical controls signals to an externaldevice.

FIG. 6B is another schematic diagram of a CMOS-SiP assembly 100, whichis similar to FIG. 6A, but shows an example structure of the electroniccircuitry 201 of the CMOS wafer 200 in more detail. Specifically, theelectronic circuitry 201 may include a logic layer 220 comprising atleast one logic circuit 222, 224 and a CMOS interconnect layer 230. TheCMOS interconnect layer 230 may comprise at a number of electricallyconductive lines 203A, 202A embedded in an electrically insulatingmaterial 204A to electrically connect the logic circuits 222, 224 with acorresponding electrically conductive line 203, 202 of the SiPinterconnect layer 310. The logic circuits 222, 224 may include a numberof transistors or logic gates or a processor, for example. Theelectrically conductive line 202 may include a via which extends atleast partially through the SiP wafer 300. In the example of FIG. 6B,the via extends all the way through the photonics layer 320 and part ofthe way through the SiP interconnect layer.

While two separate logic circuits 222, 224 are shown in FIG. 6B, inother examples there may be just one logic circuit or a larger number oflogic circuits. Likewise, there may be a large number of electricallyconductive lines and any of the logic circuits may be connected to bothelectrically conductive lines 202A and 203A.

Any CMOS compatible materials may be used for the various layers of theCMOS wafer 200 and the SiP wafer 300 described above. In one example,the photonics layer 320 includes silicon as an optical medium. Thesilicon may have been processed using semiconductor fabricationtechniques to form the photonics circuitry. The photonics circuitry mayinclude other CMOS compatible materials. For example materials having adifferent refractive index to silicon, such as silicon dioxide. Thephotonics circuitry may include germanium, germanium oxides, germaniumand silicon alloys etc for forming active or passive photonic devicesand may include electrically conductive materials to form contacts foractive photonics devices. The electrically insulating material 204 ofthe SiP interconnect layer 310 may have a lower refractive index thansilicon in order to help prevent light from leaking out of the photonicslayer 320 into the CMOS wafer. The electrically insulating material 204Aof the CMOS interconnect layer 230 may be, but does not have to be, thesame as the electrically insulating material 204 of layer 310 so as tokeep the refractive indexes and thermal expansivity of the layers thesame. In one example the electrically insulating material is adielectric such as silicon dioxide. The electrically conductive lines203, 203A, 202 and 202A may comprise any appropriate material, includingbut not limited to copper, aluminum, indium tin oxide etc.

FIG. 7 is a flow chart showing an example method 700 of manufacturing aCMOS wafer-SiP wafer assembly 100. The following description of the flowchart may be read in conjunction with FIGS. 8A-8F which are crosssectional views of the assembly 100 at various stages of themanufacturing process.

At block 710 a CMOS wafer is processed to form electronic circuitry. Theprocessing may include processing a silicon substrate 210 to formelectronic circuitry 201. The processing may include materialdeposition, etching, patterning and doping etc in order to form andconnect the various electronic components. FIG. 8A shows an example ofthe CMOS wafer 200 including a substrate 210 and an electronic circuitrylayer 201. The electronic circuitry layer may include a plurality ofelectrically conductive lines 203A and at least one electronic logiccircuit 222, both of which are embedded in an electrically insulatingmaterial 205. The electrically conductive lines 203A may connect the atleast one electronic logic circuit 222 to another electronic logiccircuit in the CMOS wafer and/or to electrically conductive contacts onan upper surface of the CMOS wafer.

At block 720 a SiP wafer is processed to form photonics circuitry. Anexample of the SiP wafer 300 is shown in FIG. 8A. The SiP wafer maystart as a silicon on insulator (SOI) wafer including a silicon layer320 over a dielectric layer 330, such as silicon dioxide, over a siliconsubstrate 340. The dielectric layer 330 is electrically insulating andmay have a lower refractive index than the silicon layer 320 so as tohelp confine light in the silicon layer 320. Photonics circuitry may beformed in the silicon layer 320, which after the formation of photonicscircuitry may be referred to as the “photonics layer”. Creating thephotonics circuitry may include semiconductor fabrication techniquessuch as material deposition, etching, patterning and doping etc. The SiPwafer further includes an electrical interconnect layer 310 positionedover the photonics layer 320. The electrical interconnect layer 310 mayinclude an electrically insulating material 204 such as silicon dioxideand a plurality of electrically conductive lines 203 embedded in theelectrically insulating material. The electrically conductive lines 203may extend to contacts on an upper surface of the SiP wafer and at leastsome of the lines 203 may connect to electrical contacts of activephotonic devices in the photonic circuitry in layer 320.

Blocks 710 and 720 may be carried out at CMOS production site. Whilethey may be carried out on the same production line, usually the CMOSwafer processing and SiP wafer processing will be carried out onseparate production lines, as photonic devices are much larger than thetransistors in modern integrated circuits and so older and cheaperequipment may be used to form the photonic circuitry.

At block 730 the SiP wafer is bonded to the CMOS wafer. This may involveany of the methods described above in relation to FIGS. 4A-4C and FIGS.6A-6B.

FIG. 8B is similar to FIG. 4C and shows the CMOS wafer 200 and SiP wafer300 of FIG. 8A after they have been bonded together to form an assembly100.

At block 740 the substrate 340 of the SiP wafer is removed. For examplethe substrate 340 may be chemically etched away. This may leave theoxide layer 330 as an exposed upper layer of the SiP wafer, as shown inFIG. 8C.

At block 750 the dielectric layer 330 is thinned or removed, for exampleby chemical etching. In other examples, the dielectric layer 330 may bemaintained at the same thickness or even thickened. Further, in someexamples the substrate 340 is not removed.

If the substrate 340 is removed and the dielectric layer 330 is thinnedor removed, this may later facilitate optical coupling between thephotonics circuitry of the photonics layer 320 and DBG semiconductorstructure 400 which is added later. Another reason for removing thesubstrate 340 and removing or thinning the dielectric layer 330, may beto reduce the distance between the electronic circuitry 201 and theupper surface of the SiP wafer. This may lead to a shorter electricallyconductive line and quicker transmission of electrical signals betweenthe electronic circuitry 201 and the DBG semiconductor structure 400.

At block 760 vias 208 are formed in the SiP wafer 300. The vias 208extend at least partially through the SiP wafer. For example the vias208 may extend through the photonics layer 320, through the dielectriclayer 330 (if it has not been removed) and through the substrate 340 (ifit has not been removed) to the upper surface of the SiP wafer. The vias208 may extend all the way through the electrical interconnect layer310, or connect with electrically conductive lines in the interconnectlayer 310, to form an electrically conductive line linking the uppersurface of the SiP wafer with the electronic circuitry 201 of the CMOSwafer.

FIG. 8D shows an example of the assembly after the vias 208 have beenformed. FIG. 8E shows another example, which is the same as FIG. 8D, butin which the dielectric layer 330 has been thinned and has a reducedthickness compared to the dielectric layer 330 in FIGS. 8A-8D. FIG. 8Fshows yet another example, which is the same as FIG. 8D, but in whichthe dielectric layer 330 has been removed.

FIG. 9 is a flow diagram showing an example method 800 of manufacturinga hybrid photonics-electronic assembly in detail. FIG. 9 may be readtogether with FIGS. 10A to 10D which show cross-sectional views of thehybrid assembly at various stages of the manufacturing process.

At block 810 an assembly 100 is received. The assembly includes a SiPwafer 300 bonded to a CMOS wafer 200. This is the same as block 110 ofmethod 10 of FIG. 1.

At block 820 a DBG semiconductor structure 400 is bonded to the receivedassembly. This is the same as block 120 of FIG. 1 and may employ any ofthe methods described above in relation to FIGS. 1, 3 and 5A to 5C.

The assembly 100 which is received at block 810 may, for example, besimilar to that shown in any of FIGS. 8D to 8F. In other examples, thereceived assembly 100 may be similar to that shown in FIG. 8C, in whichcase the vias 208 may be formed after the bonding of the DBGsemiconductor structure 400 to the SiP wafer 300. In other examples, thereceived assembly 100 may be similar to that shown in FIG. 8B, in whichcase the substrate 300 may be maintained or thinned prior to the bondingof the DBG semiconductor structure 400 to the SiP wafer 300.

FIG. 10A shows an example of the hybrid assembly after the DBGsemiconductor structure 400 has been bonded to the SiP wafer 300. TheDBG semiconductor structure 400 is similar to that shown in FIG. 5C andincludes an active layer 420 between two cladding layers 410, 430. Theselayers may be as described in relation to FIG. 5C and may comprisesimilar materials as described in relation to FIG. 5C. The DBGsemiconductor structure 400 further includes a substrate layer 440 overthe upper cladding layer 430. The substrate layer 430 may, for example,comprise an undoped DBG semiconductor material. The substrate layer mayhave been used as a handling layer to hold the DBG semiconductorstructure during in bonding process of block 820.

At block 830 the substrate layer 440 of the DBG semiconductor assemblymay be removed. The resulting structure after removal of the substratelayer 440 is shown in FIG. 10B.

At block 840 the DBG semiconductor structure 400 may be etched. Theetching may be to form an optical structure to confine light in anactive region of the DBG semiconductor structure. An example of thestructure after etching is shown in FIG. 10C. It can be seen that, inthis example, the upper cladding layer 430 and the active layer 420 arenarrower than the lower cladding layer 410. This may help to confinelight within an optical mode of the active layer 420 as the refractiveindex of the active layer 420 may be higher than the surrounding air, orhigher than a surrounding layer which is deposited later.

At block 850 a passivation layer 450 is deposited over the DBGsemiconductor structure 400. The passivation layer 450 may for examplebe a dielectric or polymer material and may electrically isolate andmechanically protect the DBG semiconductor structure. Further, asmentioned above, the passivation layer may have a lower refractive indexthan the active layer 420 and the cladding layers 410, 430 so as toconfine light within the DBG semiconductor structure. An example of theassembly after depositing the passivation layer is shown in FIG. 10D.

At block 860 an electrically conductive material is deposited toelectrically connect the DBG semiconductor assembly 400 to theelectronic circuitry 201 in CMOS wafer. This may, for example, includeforming electrical contacts of the DBG semiconductor structure andconnecting these electrical contacts to the vias 208. Block 860 mayinclude a plurality of etching and deposition processes to achieve thedesired electrical connections. FIG. 10E shows an example of an assembly540 in which electrical connections 461, 462 are formed to connect upperand lower layers of the DBG semiconductor assembly to vias 208. Thus, byapplying an electric potential between the connections 461, 462 theelectronic circuitry 201 may apply a potential difference across theactive layer 420 of the DBG semiconductor structure.

In some implementations, there may be one or more further vias, similarto the vias 208 shown in FIG. 10E. These further vias may be extendedthrough the passivation layer 450 as well as the at least part of theSiP wafer 300 in order to connect the electronic circuitry 201 with oneor more external electrical contacts (not shown) on an outside surfaceof the assembly 540. These electrical external electrical contacts andfurther vias may be used to route electrical power from an externalpower supply to the electronic circuitry 201, to route electric controlsignals from an external device to control the electronic circuitry 201,or to send electrical signals from the electronic circuitry 201 to anexternal device.

In the example shown in FIGS. 10A to 10E, a blank epitaxial die 400 forforming a DBG laser was bonded to the SiP wafer in FIG. 10B andsubsequently processed to form a DBG laser as shown in FIG. 10E. Inother examples a partially or fully pre-processed DBG laser may bebonded to the SiP wafer. In that case, depending on the extent ofpre-processing, some or all of blocks 830 to 850 need not take place. Inthe case of a fully pre-processed DBG laser, electrical connection ofthe laser to the vias 208 may still be performed, although theelectrical contact pads of the DBG laser may already been in place.

While a single die of the CMOS and SiP wafers has been shown in thefigures above, it is to be understood that the CMOS wafer may include aplurality of electronic integrated chips and the SiP wafer may include aplurality of integrated photonic chips. The process blocks of FIG. 7 maybe carried out at the wafer level, where each wafer includes a pluralityof integrated chips. The process blocks of FIG. 9 may be carried out atthe wafer level or the chip level. In one example, at least blocks 810and 820 are carried out at the wafer level for enhanced processefficiency. Blocks 830 to 850 may be carried out at either the waferlevel or the chip level.

FIGS. 11A to 11D show cross sectional examples of stages in themanufacturing process when carried out at the wafer level.

Thus, FIG. 11A shows bonding of a DBG wafer 401 including a plurality ofDBG semiconductor structures 400A, 400B, 400C on a common substrate 440to a CMOS-SiP wafer assembly 100. The assembly 100 comprises a SiP wafer300 bonded to a CMOS wafer 200. The SiP wafer includes a plurality ofphotonic integrated circuits 300A, 300B, 300C, while the CMOS wafer 200includes a plurality of electronic integrated circuits 200A, 200B, 200C.The SiP wafer 300 is bonded to the CMOS wafer 200 and they may share thesame substrate 210. Each respective electronic integrated circuit 200A,200B, 200C in the CMOS wafer 200 may be electrically connected to arespective photonic integrated circuit 300A, 300B, 300C in the SiP wafer300.

FIG. 11B shows the resulting hybrid photonics-electronic wafer assembly501 after the DBG wafer 401 has been bonded to the CMOS-SiP waferassembly 100. While the electronic integrated circuits 200A, 200B, 200Cand photonic integrated circuits 300A, 300B, 300C were shownschematically in FIG. 11A, they are shown in a greater level of detailin FIG. 11B, similar to that of FIGS. 10A to 10E. Each electronicintegrated circuit and photonic integrated circuit may have any of thefeatures discussed above in relation the CMOS wafer and SiP wafer, forinstance but not limited to the features described with reference toFIGS. 4C to 6B, 8A to 8F and 10A to 10E.

The DBG semiconductor structures 400A, 400B, 400C may be photonicdevices or dies which may be processed to form photonic devices. Theymay have any of the features of the DBG semiconductor structuresdescribed above, for example with reference to but not limited to thatdescribed in relation to FIG. 5C and FIGS. 10A to 10E. As a result ofthe bonding in FIG. 11A, or as a result of further processing carriedout after the bonding of FIG. 11A, each respective DBG semiconductorstructure 400A, 400B, 400C of the DBG semiconductor wafer 401 isoptically coupled to a respective photonic integrated circuit 300A,300B, 300C of the SiP wafer 300.

FIG. 11C shows the hybrid photonics-electronic wafer assembly 501 aftereach DBG photonic device 400A, 400B, 400C has been electricallyconnected to a respective electronic integrated circuit 200A, 200B,200C.

FIG. 11D shows the hybrid photonics-electronic wafer assembly 501 beingcut into separate hybrid photonics-electronics integrated chips.

In the example of FIGS. 11A to 11D each process is carried out at thewafer level. However, in other examples, the order of the electricalconnection and the cutting into separate chips may be reversed. Thus, inother examples, the hybrid photonics-electronic wafer assembly may becut into separate hybrid photonics integrated chips before individuallyconnecting each DBG photonic device to a corresponding electronicintegrated circuit.

12A is a schematic cross sectional view of a hybridphotonics-electronics integrated chip formed by the above methods.

The hybrid photonics-electronics integrated chip includes acomplementary metal-oxide-semiconductor (CMOS) layer 200, a siliconphotonics (SiP) layer 300 bonded to the CMOS layer 200 and a directbandgap (DBG) semiconductor layer 405 bonded to the SiP layer 300. TheCMOS layer 200 includes electronic circuitry 201. The SiP layer includesphotonics circuitry 301.

The DBG semiconductor layer 405 includes a DBG semiconductor photonicsdevice 400 which is optically coupled 302 to the photonics circuitry 301of the SiP layer 300.

An electrically conductive line 202 connects the electronic circuitry201 of the CMOS layer to an electrical contact 460 of the DBGsemiconductor photonics device 400. In this way the electronic circuitrymay control the DBG semiconductor photonics device and/or receive asignal from the DBG semiconductor device. For instance, in one examplethe electronic circuitry is electronic control circuitry to control alight emitting DBG semiconductor device. In another example theelectronic circuitry is electronic circuitry to receive and process asignal from a light detecting photonic device such as a photodetector.

The electrically conductive line 202, which connects the electroniccontrol circuitry 201 with the electrical contact 460 of the DBGsemiconductor photonics device 400, may include an electricallyconductive via which extends at least partially through the SiP layer300.

FIG. 12B is a schematic cross sectional view of another example hybridphotonics-electronics integrated chip, which is similar to the chip ofFIG. 12A except that it does not include an electrically conductive line202 to connect the electronic control circuitry 201 with the DBGsemiconductor photonics device 400. Instead, there is an electricallyconductive line 203 which connects the electronic control circuitry 201of the CMOS layer to the photonics circuitry 301 in the SiP layer 300.In this way the electronic control circuitry 201 may control and/orreceive data or other signals from the photonics circuitry 301.

FIG. 12C is a schematic cross sectional view of another example hybridphotonics-electronics integrated chip, which is similar to the chip ofFIG. 12A, but includes both an electrically conductive line 202 whichconnects the electronic control circuitry 201 with the DBG semiconductorphotonics device 400 and an electrically conductive line 203 whichconnects the electronic control circuitry 201 with the photonicscircuitry 301.

In the above examples, the SiP layer 300 may comprise a photonics layerand an electrically insulating oxide layer. The photonics layer includesthe photonics circuitry, while the electrically insulating oxide layeris positioned under the photonics layer and above the CMOS layer. Aplurality of electrically conductive lines may be embedded in theelectrically insulating oxide layer and may connect the electroniccontrol circuitry of the CMOS layer to at least one of the photonicscircuitry 301 and the DBG semiconductor photonics device 400.

In examples of the present disclosure, the optical coupling 302 may beby virtue of an optical structure which couples light in one direction,or both directions, between the DBG semiconductor photonics device 400and the photonics circuitry 301. The optical coupling structure maycouple light vertically between the DBG semiconductor photonics deviceand the photonics circuitry in the SiP layer. In this context “couplelight vertically” means couple the light into a layer above or into alayer below and includes coupling at various angles to the horizontal.Vertical coupling is in contrast to butt coupling which is couplinglight horizontally from one component to another in the same plane. Theoptical coupling structure of the present disclosure may include, but isnot limited to any of the following structures: an evanescent couplingstructure, a grating, a mirror and an angled facet of the DBGsemiconductor device. Various examples will now be described withreference to FIGS. 13-16.

FIGS. 13 and 14 show an example of evanescent coupling. Evanescentcoupling is coupling due to the evanescent field generated by a lightwave. For instance, evanescent coupling may occur between two waveguideswhich are close together, such that the evanescent field generated by alight wave in one waveguide overlaps with the other waveguide. Thusevanescent coupling may occur between two photonic devices which arenext to each other, or separated by a thin layer of material having alow refractive index.

Evanescent coupling may, for example, occur when an optical mode of theDBG semiconductor structure overlaps an optical mode of a photonicdevice in the photonic circuitry. An optical mode is the spatialdistribution of light in a direction perpendicular to its direction ofpropagation in an optical medium. Light in a photonic device adopts oneor more optical modes which are characteristic of the photonic device.An example of evanescent coupling will now be explained further withreference to FIGS. 13 and 14.

FIG. 13 is a cross sectional example of an assembly according to thepresent disclosure and is similar to FIG. 10D. Like reference numeralsindicate like parts as in FIG. 10D. It is to be understood thatconductive lines to connect the DBG photonics device 400 to vias 280 maybe present, but are not shown in order to preserve the clarity of thediagram. The dashed line 600 indicates an optical mode of the DBGsemiconductor photonics device 400. As can be seen, the optical mode 600centers on the active region 420 of the photonics device 400. However,the optical mode overlaps with the photonic circuitry in photonics layer320. This part of the optical mode, which overlaps the dielectric layer330 and the photonic layer 320, is referred to as the evanescent fieldof the light.

FIG. 14 is a close up of the upper part of FIG. 13 and shows how theoptical mode 600 overlaps with a photonic device 322 in the photonicslayer 320. The photonics circuitry in layer 320 includes at least thephotonic device 322 and may include other photonic devices as well. Thephotonic device 322 may, for example, be a waveguide. The evanescentfield of the optical mode 600 overlaps with the photonic device 322 andexcites an optical mode 610 in the photonic device 322. The optical mode610 is shown in FIG. 14 by the ellipsoid 610 which is shaded with dots.This phenomena is known as evanescent coupling. In order for evanescentcoupling to take place the DBG photonics device 400 and the photonicdevice 322 should be close enough that they have optical modes whichoverlap. Evanescent coupling is also affected by the refractive indexand relative thickness of any material, such as dielectric layer 330,which lies between the DBG photonics device 400 and the photonic device322. Evanescent coupling is more likely where any such intermediatelayer 330 is relatively thin and has a relatively low refractive indexcompared to the refractive indexes of the cores of the photonic devices400, 322. For this reason, in some examples, the dielectric layer 330may be thinned or even removed, as mentioned in block 750 of FIG. 7, aswell as shown in FIGS. 8E and 8F.

In some examples the evanescent coupling structure may be formed as aresult of bonding the DBG semiconductor structure 400 to the SiP wafer300. For example, if the DBG semiconductor structure 400 and a photoniccomponent 322 of the photonic circuitry are close enough when the DBGthen this may form an evanescent coupling structure. In other examples,the evanescent coupling structure may not exist immediately afterbonding the DBG semiconductor structure 400 to the SiP wafer, but may becreated by subsequent processes. For instance, in some examples, etchingthe DBG semiconductor structure 400 may create an optical mode whichoverlaps with the photonic circuitry, while in other examples anoverlapping optical mode may exist even before etching.

Evanescent coupling is one type of optical path which may link the DBGsemiconductor structure 400 with the photonic circuitry 301. Other typesof optical coupling structure include optical paths comprising agrating, mirror or angled facet etc. Examples are shown in FIGS. 15 and16.

FIG. 15 is a close up of the upper part of a hybrid photonic electronicintegrated assembly according to the present disclosure, similar to FIG.14. However, while FIG. 14 showed evanescent coupling, in FIG. 15 theoptical coupling is by a path including an angled facet 412 positionedat one end of the DBG photonic device 400. The angled facet 412 directslight 620 from an optical mode 600 of the DBG photonic device, downwardinto the layers below by virtue of internal reflection. The light 620 isreceived by a grating 324 of the photonic circuitry in layer 320 and maybe directed by the grating 324 to another photonic device 322, such as awaveguide, in layer 320.

FIG. 16 is similar to FIG. 15, except that instead of a grating 324, thelight 620 is received by an angled facet 326 and directed into awaveguide 322 of the photonic layer 320. In other examples the gratingor angled facets described above may be replaced by mirrors.

While the above examples have been described in relation to transferringan optical signal from the DBG semiconductor structure to the photoniccircuitry in the SiP wafer, it will be understood that similartechniques could be used to transfer light from the photonic circuitryto the DBG semiconductor structure.

Examples structures of DBG semiconductor lasers will now be described.FIG. 17 is similar to FIG. 10E and shows a cross section in the X-Yplane of an example device comprising a DBG semiconductor laser which isbonded to an assembly comprising a SiP layer 300 and CMOS layer 200, asdescribed in the earlier examples. Like numerals denote like parts as inFIG. 10E. The laser may for example be a horizontal cavity laser or avertical cavity surface emitting laser (VCESL).

FIG. 18 shows a cross section in the Y-Z plane of the device of FIG. 17,in the case that the laser is a horizontal cavity laser. Like referencenumerals denote like parts as in FIG. 17. For clarity, the detailedstructure of the electrical interconnect layer 310 and the electroniccircuitry layer 201 are not shown. The arrow 630 shows the generaldirection of light confined horizontally in the laser cavity along the Zdirection. The light may be mostly confined to the active layer 420 andreflect back and forth between the ends of the laser so that lasingoccurs. A portion of the laser light is coupled to the photoniccircuitry in layer 320 as shown by the arrow 640.

FIG. 19 shows a cross section in the Y-Z plane of the device of FIG. 17,in the case that the laser is a VCESL. Like reference numerals denotelike parts as in FIG. 17. For clarity, the detailed structure of theelectrical interconnect layer 310 and the electronic circuitry layer 201are not shown. The arrow 630 shows the general direction of lightconfined vertically in the laser cavity along the Y direction. The lightmay reflect back and forth between the ends of the laser and beamplified in the active region 420 so that lasing occurs. A portion ofthe laser light is coupled to the photonic circuitry in layer 320 asshown by the arrow 640.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the blocks ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or blocksare mutually exclusive. Furthermore, except where explicitly statedotherwise or where the context or logic demands otherwise, the processesdescribed herein may be carried out in any order and are not limited tothe specific order shown in the particular examples. Some the processesor method blocks described herein may be carried contemporaneously witheach other.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example of a generic series of equivalent or similarfeatures.

What is claimed is:
 1. A method comprising: receiving an assemblycomprising a silicon photonics (SiP) wafer bonded to a complementarymetal-oxide-semiconductor (CMOS) wafer, wherein the SiP wafer includesphotonics circuitry and the CMOS wafer includes electronic circuitry;and after receiving the assembly: bonding a direct bandgap (DBG)semiconductor structure to the SiP wafer such that the SiP wafer isdisposed between the CMOS wafer and the DBG semiconductor structure;optically coupling the direct bandgap (DBG) semiconductor structure tothe photonics circuitry; and electrically connecting the DBGsemiconductor structure to the electronic circuitry of the CMOS wafer.2. The method of claim 1 wherein the SiP wafer comprises a photonicslayer including the photonics circuitry and an electrical interconnectlayer including an electrically conductive line embedded in electricallyinsulating material; the electrically conductive line connecting theelectronic circuitry of the CMOS wafer with the photonics circuitry inthe photonics layer.
 3. The method of claim 1 wherein electricallyconnecting the DBG semiconductor structure to the electronic circuitryof the CMOS wafer includes connecting an electrical contact of the DBGsemiconductor structure with a via which extends at least partiallythrough the SiP wafer.
 4. The method of claim 1 wherein the DBGsemiconductor structure includes an active layer and at least onecladding layer.
 5. The method of claim 1 comprising processing the DBGsemiconductor structure to form a laser, a photodiode, an opticalmodulator, an optical amplifier or another type of active photonicsdevice.
 6. The method of claim 5 wherein the processing includes etchingthe DBG semiconductor structure to form an optical structure to confinelight in an active region of the DBG semiconductor structure.
 7. Themethod of claim 1 wherein the DBG semiconductor structure includes agroup III-V material.
 8. The method of claim 1 wherein the bonding ofthe DBG semiconductor structure to the SiP wafer is by molecule bonding.9. The method of claim 1 comprising forming an optical path to couplethe DBG semiconductor structure to the photonics circuitry, the opticalpath including at least one of an evanescent coupling structure, agrating, a mirror and an angled facet.
 10. The method of claim 1comprising bonding a SiP wafer to a CMOS wafer to form the assembly. 11.The method of claim 10 comprising, after bonding the SiP wafer to theCMOS wafer, removing a silicon substrate of the SiP wafer.
 12. Themethod of claim 10 comprising, after bonding the SiP wafer to the CMOSwafer, thinning or removing a dielectric layer of the SiP wafer.
 13. Themethod of claim 1 wherein the SiP wafer includes a plurality of photonicintegrated chips, the CMOS wafer includes a plurality of electronicintegrated chips and bonding the DBG semiconductor structure to the SiPwafer includes bonding a DBG wafer comprising a plurality of DBGsemiconductor structures to the SiP wafer; and wherein the methodincludes optically coupling each respective DBG semiconductor structureto a respective photonic integrated chip.
 14. A hybrid photonicselectronics integrated chip comprising: a complementarymetal-oxide-semiconductor (CMOS) layer including electronic controlcircuitry; a silicon photonics (SIP) layer bonded to the CMOS layer, theSiP layer including photonics circuitry; a direct bandgap (DBG)semiconductor layer bonded to the SiP layer such that the SiP layer isdisposed between the CMOS layer and the DBG semiconductor layer, the DBGsemiconductor layer including a DBG semiconductor photonics device whichis optically coupled to the photonics circuitry of the SiP layer; and anelectrically conductive line connecting the electronic circuitry of theCMOS layer to the photonics circuitry or to an electrical contact of theDBG semiconductor photonics device.
 15. The integrated chip of claim 14wherein the electrically conductive line includes a via which extends atleast partially through the SiP layer and connects the electroniccircuitry in the CMOS layer with the electrical contact of the DBGsemiconductor photonics device.
 16. The integrated chip of claim 14wherein the SiP layer includes a photonics layer that includes thephotonics circuitry, an electrically insulating layer which ispositioned under the photonics layer and above the CMOS layer; and aplurality of electrically conductive lines embedded in the electricallyinsulating layer and connecting the electronic circuitry of the CMOSlayer with the photonics circuitry and with the DBG semiconductorphotonics device.
 17. The integrated chip of claim 14 comprising astructure to couple light vertically between the DBG semiconductorphotonics device and the photonics circuitry in the SiP layer.
 18. Ahybrid photonics-electronics wafer assembly comprising: a complementarymetal-oxide-semiconductor (CMOS) wafer including a plurality ofelectronic integrated circuits; a silicon photonics (SiP) wafer bondedto the CMOS wafer, the SiP wafer including a plurality of photonicintegrated circuits; a direct bandgap (DBG) semiconductor wafer bondedto the SiP wafer such that the SiP wafer is disposed between the CMOSwafer and the DBG semiconductor wafer, the DBG semiconductor waferincluding a plurality of photonic devices; wherein each respectivephotonic device of the DBG semiconductor wafer is optically coupled to arespective photonic integrated circuit of the SiP wafer.
 19. The hybridphotonics-electronics wafer assembly of claim 18 wherein each photonicdevice of the direct bandgap semiconductor wafer is electrically coupledto a respective electronic integrated circuit of the CMOS wafer.
 20. Thehybrid photonics-electronics wafer assembly of claim 18 wherein eachphotonic integrated circuit of the SIP wafer is electrically coupled toa respective electronic integrated circuit of the CMOS wafer.